Positron emission tomography (PET) is a non-invasive medical imaging technique which utilizes specialized tracers to depict both physioligic and pathophysiologic processes. The aim of this proposal is to apply PET technology for the detection, characterization, and assessment of the response to therapy of tumors derived from the sympathetic nervous system in adults, and these tumors and other solid malignancies in children. We expect to show, by virtue of the superior image resolution of PET technology, it is anticipated that serial studies will show that changes in tumor uptake reflect the tissue response to treatment and serve as an early indicator of therapeutic efficacy or failure. If such information can be made available noninvasively by PET scanning, the management of patients with tumors could be substantially improved.